yet another inverse function I wrote before, though it applies for only 1D
array.
typedef struct _enuminfo{ArrayType *data;char *ptr;int16 typlen;bool typbyval;char
typalign;
} EnumInfo;
Datum array_enum(PG_FUNCTION_ARGS){FuncCallContext *funcctx;MemoryContext oldcontext;ArrayType *input;EnumInfo
*info;Datum result;if(SRF_IS_FIRSTCALL()){ funcctx = SRF_FIRSTCALL_INIT(); oldcontext =
MemoryContextSwitchTo(funcctx->multi_call_memory_ctx); input = PG_GETARG_ARRAYTYPE_P(0); if(ARR_NDIM(input)
!=1){ elog(ERROR, "array_enum() accepts only one dimension
array."); } funcctx->max_calls = ArrayGetNItems(ARR_NDIM(input),
ARR_DIMS(input)); info = (EnumInfo*)palloc0(sizeof(EnumInfo)); info->data =
(ArrayType*)PG_DETOAST_DATUM_COPY(input); info->ptr = ARR_DATA_PTR(info->data); get_typlenbyvalalign(
info->data->elemtype, &(info->typlen), &(info->typbyval), &(info->typalign) );
funcctx->user_fctx= info; MemoryContextSwitchTo(oldcontext);}funcctx = SRF_PERCALL_SETUP();info =
funcctx->user_fctx;if(funcctx->call_cntr< funcctx->max_calls){ /* Get source element */ result =
fetch_att(info->ptr,info->typbyval, info->typlen);
info->ptr = att_addlength(info->ptr, info->typlen,
PointerGetDatum(info->ptr)); info->ptr = (char *) att_align(info->ptr, info->typalign); SRF_RETURN_NEXT(funcctx,
result);}else{ SRF_RETURN_DONE(funcctx);}
}
Hitoshi Harada
> -----Original Message-----
> From: pgsql-hackers-owner@postgresql.org
> [mailto:pgsql-hackers-owner@postgresql.org] On Behalf Of Joe Conway
> Sent: Tuesday, January 29, 2008 11:00 AM
> To: Jeff Davis
> Cc: Neil Conway; pgsql-hackers
> Subject: Re: [HACKERS] RFC: array_agg() per SQL:200n
>
> Jeff Davis wrote:
> > On Sun, 2008-01-27 at 22:11 -0800, Neil Conway wrote:
> >> p. 564 discusses the required behavior. The result of array_agg() is an
> >> array with one element per input value, sorted according to the optional
> >> ORDER BY clause. NULL input values are included in the array, and the
> >> result for an empty group is NULL, not an empty array. Note that per
> >> page 66, I'd expect array values in the input to array_agg() not to be
> >> flattened.
> >
> > Should there be an inverse operator (a SRF, in this case) that returns a
> > set from an array?
>
> Yes -- see UNNEST
>
> Joe
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match